This protocol will use PET technology to determine if isoflurane anesthesia changes binding of 11C-flumazenil, a GABA agonist, to its receptor in different regions of the brain. Binding will be measured by the Bmax/KD quotient. This study will determine if isoflurane anesthesia changes the binding of the GABA antagonist midazolam in the interaction studies using combinations of 11C-flu-mazenil, unlabeled midazolam and isoflurane anesthesia.